DE 41 09 118 C2 describes a method for an automatic evaluation of a substance contained in a water sample, wherein a laboratory analysis cuvette comprises an optical identification in the form of a barcode. The associated laboratory analyzer comprises a cuvette chamber with a cuvette rotating device. A reading device is further provided in the cuvette chamber, by means of which the cuvette barcode can be read out, while the cuvette is rotated in the cuvette chamber by the cuvette rotating device. The reading device scans in a punctiform manner. Locating the barcode takes relatively long in adverse conditions since the start of the barcode first needs to be located.